feat(node-player): use Service Worker for auth, enable streaming playback

Add a Service Worker that intercepts /api/* requests and injects the
Bearer token. This allows <audio> and <img> elements to use direct
URLs instead of downloading entire files as blobs first.

- Audio now streams progressively (no full download before playback)
- Cover art loads via regular <img src> (SW adds auth header)
- Remove blob-based preloadStream, fetchCoverBlob, useCoverUrl hook
- Register SW in main.tsx, token synced via postMessage

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

furumi-node-player/client/src/main.tsx

@@ -5,6 +5,10 @@ import { store } from './store'
 import './index.css'
 import App from './App.tsx'
 
+if ('serviceWorker' in navigator) {
+  navigator.serviceWorker.register('/sw.js')
+}
+
 createRoot(document.getElementById('root')!).render(
   <StrictMode>
     <Provider store={store}>